The present invention relates to an in-mold molded project with a matted surface that defines a lusterless finish and that is resistant to damage and stain because of an excellent matted effect produced in a so-called in-mold molding operation, and to a method for manufacturing the in-mold molded product.
Conventionally, methods which are available for manufacturing molded products having matted surfaces are as follows:
(1) In one method, the surface of a molded product is locally masked, and then either matting paint or surface-lustering paint is applied to the surface of the molded product by a spray coating process to obtain a product which is locally provided with both matted and lustered regions. If the molded product is to include a superficial design such as characters or a pattern, a further process such as screen printing, plug printing, or hot-stamping must be executed. On the other hand, if the molded product has a complex surface with projections and recesses, then it is difficult to mask such surface to prevent the coated paint from infiltrating the masked regions. Thus, the masking process takes much time and results in the impossibility of utilizing mass production. Therefore, application of this method is limited to the production of those molded products having a simple configuration close to planar. PA1 (2) A second conventional method separately constructs matted and lustered component parts. For example, lustered component parts are made of polyvinyl chloride sheets, metallic parts, or resin-molded parts. On the other hand, those component parts to be provided with a lusterless or matted surface are produced by a mold unit having a grained surface. Finally, these component parts are integrated into a complete product locally having matted and lustered regions. Thus, this conventional method can only be employed for the production of those molded products having a simple configuration, and therefore freedom of design is restrained. In addition, production of the product involves a high cost on the part of the manufacturer.
There is also an in-mold molding method available for the production of molded products having matted surfaces. This method involves the following steps.
First, a mat transfer member capable of forming fine projections and recesses for producing a matted effect is secured at a predetermined position inside of an injection mold unit. Next, the mold unit is closed and resinous material is injected therein to cause the mat transfer member to tightly adhere to the surface of the molded member simultaneously with the formation thereof. Finally, a substrate sheet of the mat transfer member is stripped off, thereby to result in the molded product.
Substantially, the mat transfer member is composed of either of the following: a transfer member including a release layer, a pattern layer, and an adhesive layer which are sequentially stratified on the substrate sheet having a surface preliminarily matted by a process such as sand blasting, i.e. defining an irregular surface, or chemical etching; or a transfer member including a release layer, a pattern layer, and an adhesive layer which are sequentially stratified on the substrate sheet which is constructed to form by printing, on a surface preliminarily lustered, a projected and recessed layer, by use of a material such as a loading pigment, having a finely projected and recessed surface.
After completing adhesion of the transfer layer of the mat transfer member to the molded member, either the substrate sheet or the substrate sheet together with the projected and recessed layer are stripped off and removed therefrom. The projections and recesses of the substrate sheet or the projected and recessed layer thereby are transferred onto the release layer to form fine projections and recesses on the surface of the release layer, and as a result, the surface of the in-mold molded product is matted.
Nevertheless, the molded product produced by employing the in-mold molding process described above has proved to have poor surface-wear characteristics because streaks easily can be generated merely by scratching the matted surface by a fingernail. Likewise, there is the problem that fingerprints will remain on the matted surface without being erased at all. Probably this is because a stain such as caused by sebum from the skin of a finger adheres to the matted surface of the molded product to vary the light scattering effect on the fine projections and recesses in the matted regions, thus eventually varying the matted effect. This is a phenomenon similar to that which occurs when water drops on a ground glass surface wherein a certain difference is generated between a region without water and a matted region holding water. Therefore, conventionally, although it is desired to provide matted designs on in-mold molded products, such designs cannot practically be applied to any objects that will be within easy access of human fingers because of fear of substantial degradation of the matted effect caused by adhered stains.
Furthermore, since the fine projections and recesses provided for the in-mold molded product are fully merged by the thickness of the mat transfer member itself, the matted effect cannot fully be provided on surfaces of those inserted molded pieces produced by employing an in-mold molding unit grained by an etching process and a conventional transfer member.
The object of the present invention is to fully resolve the problems described above by providing a novel in-mold molding product having excellent surface-wear characteristics and having a surface fully matted and resistant to stain, and by providing a novel method for manufacturing such products.